Abstract
The polar bear (Ursus maritimus) is the only Arctic land mammal that dives into 27 water to hunt. Despite thermal insulation provided by blubber and fur layers and low Arctic 28 temperatures, their fur is typically observed to be free of ice. This study is the first to investigate 29 the anti-icing properties of polar bear fur. Here, we show that polar bear fur exhibits low ice 30 adhesion strengths comparable to fluorocarbon-coated fibers, with the low ice adhesion a 31 consequence of the fur sebum (hair grease). Lipid analyses reveal the presence of cholesterol, 32 diacylglycerols, anteisomethyl-branched fatty acids, and the unexpected absence of squalene. 33 Quantum chemical calculations predict low ice adsorption energies for identified lipids and high 34 adsorption for squalene, suggesting sebum composition is responsible for the observed anti-icing 35 properties. Our work enhances understanding of polar bears and their interactions with their 36 environment and builds on Inuit knowledge of natural anti-icing materials.